What size do you wear? Most men’s clothing stores carry suits running into the larger sizes. If they don’t have something big enough (which I doubt), I’m sure they could tell you where you could find it.
P.S. I take my son (who is also on the heavy side to XXos (or however you spell it), which is in the parking lot underneath the Rav Shefa mall. They usually have good sales right before each YT and during bein hazmanim, but even so their prices in general are not bad.